A magnetic recording medium comprising a substrate and a magnetic layer which is formed on the substrate and consists of a thin film of a metal or a metal oxide with high coercive force has better high density recording characteristics than one comprising a magnetic layer formed by coating and drying a magnetic coating composition, namely a magnetic coating layer, on the substrate, although the former has a very flat surface and a large coefficient of friction so that it is more easily abrased or damaged when it is slid against a magnetic head and/or a guide during recording or reproducing and has poor running stability resulting in increase of fluctuation of output.
Since high density recording is increasingly required, the magnetic recording medium comprising the magnetic coating layer is being improved so as to have a thin magnetic coating layer and more smooth surface so as to increase short wavelength characteristics. Thus, it is highly required for the magnetic layer to have better abrasion resistance.
To this end, it has been proposed to coat the surface of the magnetic layer with various lubricants to form a protective film with good lubrication, or to add the lubricant to the magnetic coating layer. Thereby, a coefficient of friction is reduced so that the abrasion resistance, durability and running stability are improved. Among the lubricants, fluorine-containing lubricants such as perfluoroalkyl polyether, tetrafluoroethylene telomer, and trifluorochloroethylene resin are reported to be particularly effective.
Since, however, the fluorine-containing lubricant has very weak interaction with the surface of the magnetic layer, it tends to become removed from the surface in use and its lubricating effect is not always demonstrated. In addition, under the circumstance where the magnetic recording medium is slid on the magnetic head at a high speed, viscosity resistance of the lubricant increases so that the running stability of the medium is deteriorated and, in turn, fluctuation of the output is increased. Furthermore, when the fluorine-containing lubricant is coated on the surface of the magnetic layer consisting of a thin layer of ferromagnetic metal or metal oxide, the recording medium sticks to the magnetic head or the guide and running of the medium is stopped if both surfaces of the magnetic layer and the magnetic head or the guide are extremely smooth.